Recently, there has been frequent theft of a construction machine such as a hydraulic excavator. Under such a situation, a variety of security systems have been proposed for a construction machine.
According to a technology described in JP-B-2642455, operation of a start blocking section for an engine start system is released only when a predetermined password is entered to a key input device in an appropriate order thus permitting operation of a construction machine, thereby disabling operation by a third party who does not know the password and preventing theft of the construction machine.
Japanese Patent Laid-Open No. 44938/1998 proposes a security system capable of arbitrarily setting or erasing a password by using a special magnetic rod.
According to a security system described in Japanese Patent Laid-Open No. 50584/1997, for example, when a predetermined personal identification number is entered from a key input device, a pilot hydraulic source communicates with a pilot valve to permit operation of hydraulic apparatus, while the pilot hydraulic source and the pilot valve are blocked from each other to inhibit the operation of the hydraulic apparatus when the personal identification number is not input or a wrong number is entered. An IC card may be inserted instead of key input to permit operation of the hydraulic apparatus.
According to a security system described in Japanese Patent Laid-Open No. 301072/1996, for example, in case where a predetermined personal identification number is not input from a key input device, a starter circuit is not activated by a starting operation and starting of the engine is inhibited.
In general, for a construction machine such as a hydraulic excavator, there are often cases where a third party other than a regular operator of the construction machine is obliged to operate the construction machine. For example, in case where a construction machine is transported between work sites apart from each other, the construction machine is conveyed on a trailer. In this case, loading/unloading of a construction machine onto/out of a trailer is often carried out by a handler such as a delivery agent or a maintenance person, not an operator of the construction machine.
In case such a third party operates a construction machine equipped with a security system described in the aforementioned documents, the operator of the construction machine must give the password to the handler as required. However, presenting a password to a third party leads to leakage of a password, causing a serious security problem.
According to a related art technology described in the Japanese Patent Laid-Open No. 44398/1998, setting of a new password is made possible by inserting a magnetic rod. This allows a password given to a handler other than an operator to be changed afterwards using the magnetic rod. Such change of a password prevents leakage of the password. However, frequent change of a password is not favorable because it is cumbersome to an operator and may confuse the operator.
According to security systems described in the Japanese Patent Laid-Open No. 50584/1997 and the Japanese Patent Laid-Open No. 301072/1996, a key input device or card reader dedicated to a construction machine must be installed. This results in additional costs.
The problem with the related art technology described in the aforementioned documents is that input of a password is made by a site worker such as an operator or handler of the construction machine.